Hydraulic pressure control apparatus

ABSTRACT

A hydraulic pressure control apparatus includes a first pressure regulating valve for reducing an initial oil pressure of a working oil introduced from an inlet port, a solenoid-operated valve, and a second pressure regulating valve for converting the initial oil pressure of the working oil into an actuating pressure. The three valves share a single body. A joining boss and a relief valve, which is operable to release the working oil out of a passage in the body when the pressure of the working oil in the passage becomes equal to or greater than a predetermined threshold value, are arranged on a closed end face of the body. The joining boss and the relief valve have respective upper surfaces that are covered by a cover.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-114733 filed on May 30, 2013, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic pressure control apparatushaving a relief valve, which is capable of being opened if the pressureof a working oil becomes equal to or greater than a predeterminedthreshold value.

2. Description of the Related Art

One known type of hydraulic pressure control apparatus is disclosed inJapanese Laid-Open Patent Publication No. 05-345528. The disclosedhydraulic pressure control apparatus serves to regulate the pressure ofa working oil that is supplied to the clutch of an automobile. Thehydraulic pressure control apparatus includes a differential clutchcontrol valve and a solenoid modulator valve that function as pressureregulating valves, and a single linear solenoid-operated valve. Theinitial pressure (line pressure) of the working oil is reduced to apredetermined pressure by the solenoid modulator valve, and the reducedoil pressure is supplied to the linear solenoid-operated valve.

The linear solenoid-operated valve generates a solenoid pressure basedon an electric current that is supplied to the solenoid thereof, and thesolenoid pressure is supplied to the differential clutch control valve.Based on the solenoid pressure, the differential clutch control valveconverts the line pressure, and the working oil is supplied to theclutch under the converted pressure, which acts as a predeterminedclutch pressure (actuating pressure).

According to Japanese Laid-Open Patent Publication No. 05-345528, amongthe three valves that function as described above, it has been proposedthat the differential clutch control valve and the solenoid modulatorvalve are arranged in parallel facing relation to each other within avalve body, which is made up of a combination of a lower valve body andan upper valve body, whereas the linear solenoid-operated valve isarranged between the two pressure regulating valves with the axis of thelinear solenoid-operated valve extending perpendicularly to the twopressure regulating valves. Further, oil passageways for the working oilare defined in the upper valve body.

SUMMARY OF THE INVENTION

The aforementioned valve body, which is constituted from the lower valvebody and the upper valve body in combination as disclosed in JapaneseLaid-Open Patent Publication No. 05-345528, has a large wall thicknessfor ensuring sufficient mechanical strength. Therefore, a high-pressureworking oil can be supplied to the valve body. However, such a valvebody, which has a large wall thickness, fails to meet recent demands forsmaller and lighter components to be used as devices for automobiles.

It is a general object of the present invention to provide a hydraulicpressure control apparatus which has sufficient mechanical strength.

A major object of the present invention is to provide a hydraulicpressure control apparatus which can be reduced in size and weight.

According to an embodiment of the present invention, there is provided ahydraulic pressure control apparatus comprising a first pressureregulating valve configured to reduce an initial oil pressure of aworking oil introduced from an inlet port, a solenoid-operated valvesupplied with an electric current and a reduced oil pressure, the oilpressure reduced by the first pressure regulating valve, thesolenoid-operated valve configured to convert the reduced oil pressureinto a solenoid pressure in accordance with the supplied electriccurrent, a second pressure regulating valve supplied with the solenoidpressure from the solenoid-operated valve, the second pressureregulating valve converting the initial oil pressure of the working oilintroduced from the inlet port into an actuating pressure in accordancewith the solenoid pressure, and a relief valve arranged in a working oilpassage, the relief valve being openable to release the working oil outof the passage when the pressure of the working oil in the passagebecomes equal to or greater than a predetermined threshold value of therelief valve. In the hydraulic pressure control apparatus, the firstpressure regulating valve, the solenoid-operated valve and the secondpressure regulating valve share a single body, the second pressureregulating valve has an outlet passageway in the body, the relief valvehas a valve body, and the valve body is integrally molded onto the bodyand protrudes from an end face of the body at a position correspondingto the outlet passageway, the body includes a joining boss, the joiningboss is integrally molded onto the body and protrudes from the end faceof the body at a position corresponding to the second pressureregulating valve, and the joining boss extends parallel to the valvebody of the relief valve, the valve body and the joining boss are joinedto each other by a rib, the rib being thinner than the valve body andthe joining boss, and the joining boss and the valve body haverespective upper surfaces, the upper surfaces are covered by a cover,and the cover is connected by a fastener to the joining boss.

In the hydraulic pressure control apparatus, the working oil is suppliedunder high pressure to the first pressure regulating valve and thesecond pressure regulating valve. The valve body of the relief valve isarranged on the end face of the body at a position corresponding to thesecond pressure regulating valve. In addition, the joining boss, whichis connected to the cover that covers the upper surface of the reliefvalve, is arranged on the end face of the body at a positioncorresponding to the first pressure regulating valve.

Both the valve body and the joining boss are formed integrally with thebody, or stated otherwise, the valve body and the joining boss make uppart of the body. The body is reinforced by the valve body and thejoining boss and therefore possesses high mechanical strength. Even ifthe body is a single component having one or more passageways definedtherein for the working oil, the body has sufficient mechanical strengthnear the first pressure regulating valve and the second pressureregulating valve, which are supplied with the working oil under highpressure. Therefore, the body can be reduced in size and weight whilemaintaining a high level of mechanical strength.

The valve body and the joining boss may be formed so as to extend alonga direction in which a casting die assembly for casting the body isopened. Therefore, the body can be produced with ease.

The valve body of the relief valve may accommodate a valve element and aresilient member therein, the resilient member has an end seated ontothe cover, and the valve element is resiliently biased so as to beseated on a valve seat by the resilient member.

In this manner, the relief valve is highly simple in structure, andhence assembly thereof can be performed easily and conveniently.

The valve joining boss may have a protruding height greater than that ofthe valve body, and the cover may be spaced from the upper surface ofthe valve body. In this case, working oil that has leaked into a reliefchamber in the relief valve is discharged through a clearance formedbetween the cover and the upper surface of the valve body.

Preferably, the cover has a hook, and the valve body has an engagingportion that engages with the hook. When the cover is fastened to thejoining boss by the fastener, the cover is prevented from turning as aresult of the engaging portion that engages with the hook. Therefore,the cover can easily be installed on the body.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram of a hydraulic pressure control apparatusaccording to an embodiment of the present invention;

FIG. 2 is a perspective view, shown partially in horizontal crosssection, of the hydraulic pressure control apparatus;

FIG. 3 is a plan view of an open end face of a body of the hydraulicpressure control apparatus;

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 3;

FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 3;

FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 3;

FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 3;

FIG. 9 is a fragmentary vertical cross-sectional view of the hydraulicpressure control apparatus in the vicinity of a relief valve;

FIG. 10 is a plan view of a closed end face of the body; and

FIG. 11 is an enlarged fragmentary plan view of the closed end face ofthe body.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A hydraulic pressure control apparatus according to a preferredembodiment of the present invention will be described in detail belowwith reference to the accompanying drawings.

FIG. 1 is a system diagram of a hydraulic pressure control apparatus 10according to an embodiment of the present invention. As shown in FIG. 1,the hydraulic pressure control apparatus 10 has a regulator valve 12(first pressure regulating valve), a solenoid-operated valve 14, and acontrol valve 16 (second pressure regulating valve). Working oil isintroduced from an inlet port 18 into a first oil passageway 20 by anon-illustrated oil pump, and then the working oil is distributed fromthe first oil passageway 20 to the regulator valve 12 and the controlvalve 16.

The regulator valve 12 functions to reduce the initial pressure (linepressure) of the working oil supplied from the inlet port 18 to apredetermined pressure. More specifically, the regulator valve 12 has afirst valve rod 22 slidably arranged in a first valve hole 24, and whichis resiliently biased under a resilient biasing force of a firstpressure regulating spring 26, so as to normally close the regulatorvalve 12. The first valve rod 22 is movable back and forth in the firstvalve hole 24 in accordance with a difference in magnitude between theresilient biasing force of the first pressure regulating spring 26 and afeedback oil pressure that acts on the regulator valve 12. The firstvalve rod 22 stops at a position at which the resilient biasing force ofthe first pressure regulating spring 26 and the feedback oil pressurethat acts on the first valve rod 22 are held in equilibrium, therebyregulating the oil pressure or depressurizing the working oil.

Under the reduced pressure, the working oil is supplied through a secondoil passageway 28 to the solenoid-operated valve 14. Thesolenoid-operated valve 14 has a solenoid 30, which receives a commandelectric current supplied from a controller such as an ECU or the like.The solenoid 30 generates a thrust force in accordance with the value ofthe supplied command electric current. The solenoid-operated valve 14also has a second valve rod 32 slidably arranged in a second valve hole34. The second valve rod 32 is kept in a position at which the resilientbiasing force of a second pressure regulating spring 35, which is housedin a spring chamber 35 a, and a feedback oil pressure that acts on thesecond valve rod 32 are held in equilibrium, thereby regulating the oilpressure or depressurizing the working oil to a predetermined solenoidpressure.

Under the predetermined solenoid pressure, the working oil flows througha third oil passageway 36 to reach the control valve 16. The controlvalve 16 is supplied with the working oil, which is distributed under aline pressure from the first oil passageway 20. The control valve 16 hasa third valve rod 38 slidably arranged in a third valve hole 40. Thethird valve rod 38 is kept in a position at which the resilient biasingforce of a third pressure regulating spring 42 and a feedback oilpressure that acts on the third valve rod 38 are held in equilibrium,thereby regulating or reducing the line pressure, which is applied tothe control valve 16, to a predetermined oil pressure. Under the reducedoil pressure, the working oil flows out of the control valve 16 and isdischarged from an outlet port 44. From the outlet port 44, the workingoil may be supplied to a non-illustrated clutch, for example.

An oil passageway extends from the control valve 16 to the outlet port44, and a relief valve 46 is connected thereto, which prevents theworking oil from being supplied from the outlet port 44 to the clutch ifthe pressure of the working oil, i.e., the clutch pressure from theclutch, becomes equal to or greater than a predetermined thresholdpressure. More specifically, the relief valve 46 includes a sphericalvalve element 48 that normally is seated on a valve seat 52 under aresilient biasing force of a closing spring 50 (resilient member). Ifthe clutch pressure becomes excessively high, the working oil pressesthe spherical valve element 48 against the resilient biasing force ofthe closing spring 50. When the spherical valve element 48 is unseatedfrom the valve seat 52, thereby compressing the closing spring 50, therelief valve 46 opens in order to drain the working oil through therelief valve 46 and out of the hydraulic pressure control apparatus 10.

In FIG. 1, the reference numeral 51 denotes a drain in the control valve16.

Structural details of the hydraulic pressure control apparatus 10 willbe described below.

FIG. 2 is a perspective view, shown partially in horizontal crosssection, of the hydraulic pressure control apparatus 10. FIG. 3 is aplan view of an open end face of a body 54 of the hydraulic pressurecontrol apparatus 10. In FIG. 2 and the other figures, widthwise, axial,and thicknesswise directions the body 54 correspond to X, Y, and Zdirections, respectively. The phrase “an open end face of the body 54”refers to an end face in which the first oil passageway 20, the secondoil passageway 28, and the third oil passageway 36 are defined. Thephrase “a closed end face of the body 54” refers to an end face on aside opposite from the open end face.

As shown in FIGS. 2 and 3, the regulator valve 12, the solenoid-operatedvalve 14, and the control valve 16 are arranged together in the singlebody 54 as a valve body. The solenoid-operated valve 14 and the controlvalve 16 are arranged at opposite ends of the body 54, respectively, onboth sides of the regulator valve 12 which is interposed therebetween.

As shown in FIG. 2, the body 54 has the three valve holes 24, 34, 40defined therein. The first valve hole 24 is positioned at the center ofthe body 54, and the second and third valve holes 34, 40 are arranged onopposite ends of the body 54. The first valve hole 24, the second valvehole 34, and the third valve hole 40 are juxtaposed with respective axesthereof arrayed parallel to each other along the widthwise direction,i.e., the horizontal direction (X direction) of the body 54.

The first valve rod 22 of the regulator valve 12 is housed in the firstvalve hole 24. The second valve rod 32 of the solenoid-operated valve 14is housed in the second valve hole 34. The third valve rod 38 of thecontrol valve 16 is housed in the third valve hole 40. Therefore, theregulator valve 12, the solenoid-operated valve 14, and the controlvalve 16 are juxtaposed with respective axes thereof arrayed in parallelto each other along the widthwise direction (X direction/horizontaldirection) of the body 54. Each of the first valve rod 22, the secondvalve rod 32, and the third valve rod 38 comprises a spool.

The ends of the first valve hole 24, the second valve hole 34, and thethird valve hole 40 are closed by caps 56, 58, 60, respectively. Asshown in FIG. 4, which is a cross-sectional view taken along line IV-IVof FIG. 3, and FIG. 5, which is a cross-sectional view taken along lineV-V of FIG. 3, other ends of the first valve hole 24 and the third valvehole 40 are closed by the body 54 itself. An end of the solenoid 30 isexposed in the other end of the second valve hole 34 (see FIGS. 2 and3).

As shown in FIGS. 4 and 5, the first pressure regulating spring 26 isarranged between the first valve rod 22 and an inner wall surface of thebody 54, and the third pressure regulating spring 42 is arranged betweenthe third valve rod 38 and an inner wall surface of the body 54. Thefirst pressure regulating spring 26 and the third pressure regulatingspring 42 resiliently bias the first valve rod 22 and the third valverod 38 so as to move in directions toward the respective caps 56, 60. Asshown in FIG. 6, which is a cross-sectional view taken along line VI-VIof FIG. 3, the second pressure regulating spring 35 is arranged betweenthe cap 58 and the second valve rod 32, so as to resiliently bias thesecond valve rod 32 to move in a direction toward the solenoid 30.

As shown in FIG. 3, the inlet port 18, the first oil passageway 20, thesecond oil passageway 28, the third oil passageway 36, and the outletport 44 are defined in the open end face of the body 54. The ports andthe oil passageways are defined by a wall, which will be referred to asan “oil passageway wall” and is denoted by the reference numeral 61.

The inlet port 18 is defined near the first oil passageway 20 and thethird valve hole 40. A filter 62 is arranged in the inlet port 18 forremoving foreign matter from the working oil (see FIG. 5).

The inlet port 18 is joined to an inlet passageway 64, which is definedin the body 54 downstream of the inlet port 18, and as shown in FIG. 5,extends in a straight line along the thicknesswise direction (Zdirection) of the body 54. The depth of the inlet passageway 64 from thetop surface of the oil passageway wall 61 is greater than the depth ofthe first oil passageway 20.

The inlet passageway 64 and the first oil passageway 20 are held influid communication with each other through a communication passageway66. An upstream end of the communication passageway 66 opens into theinlet passageway 64 at a substantially central position thereof in theheightwise direction (Z direction) of the inlet passageway 64. Thecommunication passageway 66 extends obliquely to the thicknesswisedirection of the body 54, and a downstream end of the communicationpassageway 66 opens into an upstream end of the first oil passageway 20.An orifice 67 of the communication passageway 66 is located near one endthereof that opens into the first oil passageway 20.

As shown in FIG. 3, the first oil passageway 20 extends tortuously alongthe axis (Y direction) of the third valve hole 40, and bends toward thefirst valve hole 24 in the vicinity of a downstream end of the thirdvalve hole 40. The first oil passageway 20 has a downstream endpositioned over and across the first valve hole 24.

A first line pressure inlet port 68 (third valve hole line pressureinlet) is defined in the body 54 near the upstream end of the first oilpassageway 20 and in the vicinity of the downstream opening of thecommunication passageway 66. A second line pressure inlet port 70 (firstvalve hole line pressure inlet) is defined in the body 54 near thedownstream end of the first oil passageway 20. Therefore, the first linepressure inlet port 68 and the second line pressure inlet port 70 aredefined successively downstream in this order along the first oilpassageway 20. The first oil passageway 20 is held in fluidcommunication with the third valve hole 40 (see FIG. 5) through thefirst line pressure inlet port 68, and with the first valve hole 24through the second line pressure inlet port 70. Therefore, the workingoil, which is introduced from the inlet port 18 into the first oilpassageway 20, is distributed to the first valve hole 24 and the thirdvalve hole 40.

The second oil passageway 28 is defined over and across a portion of thefirst valve hole 24 as well as a portion of the second valve hole 34(see FIG. 3). The second oil passageway 28 extends substantially in astraight line along the widthwise direction (X direction) of the body54, and is shorter than the first oil passageway 20 and the third oilpassageway 36.

A first valve hole outlet hole 72 (first valve hole outlet) forreleasing the working oil out of the first valve hole 24 is defined inthe body 54 near the upstream end of the second oil passageway 28, and asecond valve hole inlet hole 74 (second valve hole inlet) forintroducing the working oil into the second valve hole 34 is defined inthe body 54 near the downstream end of the second oil passageway 28.Therefore, the second oil passageway 28 is held in fluid communicationwith the first valve hole 24 through the first valve hole outlet hole72, and is held in fluid communication with the second valve hole 34through the second valve hole inlet hole 74.

A first pool 76 is defined in the body 54 near the first oil passageway20. The third valve hole 40 and the first pool 76 are held in fluidcommunication with each other through a first communication hole 78.

As shown in FIG. 7, which is a cross-sectional view taken along lineVII-VII of FIG. 3, the body 54 has a first drain hole 80 that is definedthrough the body 54. The first pool 76 and the first drain hole 80 aredivided from each other by an overflow wall 82, the dimension of whichalong the heightwise direction (Z direction) is smaller than the oilpassageway wall 61. If the amount of working oil that flows into thefirst pool 76 is too large to be blocked by the overflow wall 82, theworking oil in the first pool 76 overflows the overflow wall 82 and isdrained from the first drain hole 80.

The third oil passageway 36 extends along the axial direction (Ydirection) of the second valve hole 34, bends toward the first valvehole 24 and the third valve hole 40, and extends over the first valvehole 24 to the third valve hole 40. Accordingly, most of the third oilpassageway 36 extends along the widthwise direction (X direction) of thebody 54.

A second valve hole outlet hole 84 (second valve hole outlet) forreleasing the working oil out of the second valve hole 34 is defined inthe body 54 at a position at which the third oil passageway 36 bendsfrom the second valve hole 34 toward the first valve hole 24. A solenoidpressure inlet hole 86 (solenoid pressure inlet) for introducing theworking oil into the third valve hole 40 is defined in the body 54 atthe downstream end of the third oil passageway 36. The third oilpassageway 36 is held in fluid communication with the second valve hole34 through the second valve hole outlet hole 84, and is held in fluidcommunication with the third valve hole 40 through the solenoid pressureinlet hole 86 (see FIG. 5).

A second pool 88 is defined in the body 54 near the third oil passageway36 (see FIG. 3). The second valve hole 34 and the second pool 88 areheld in fluid communication with each other through a secondcommunication hole 90. A damper orifice 91 is defined through the body54 in the vicinity of the second communication hole 90.

A second drain hole 92 is defined through the body 54. As shown in FIG.8, which is a cross-sectional view taken along line VIII-VIII of FIG. 3,the second pool 88 and the second drain hole 92 are divided from eachother by an overflow wall 94, the dimension of which along theheightwise direction (Z direction) is smaller than the oil passagewaywall 61. As with the first pool 76, if the amount of working oil thatflows into the second pool 88 is too large to be blocked by the overflowwall 94, the working oil in the second pool 88 overflows the overflowwall 94 and is drained from the second drain hole 92.

The outlet port 44 opens in the vicinity of the first oil passageway 20(see FIG. 3). An outlet passageway 96 is joined upstream to the outletport 44. In other words, the outlet port 44 serves as a downstreamopening of the outlet passageway 96. As shown in FIG. 9, which is afragmentary vertical cross-sectional view of the hydraulic pressurecontrol apparatus 10 near the relief valve 46, i.e., a cross-sectionalview taken along line IX-IX of FIG. 10, the outlet passageway 96 extendsin a straight line along the thicknesswise direction of the body 54, andlies perpendicularly across the third valve hole 40 at a substantiallycentral position in the axial direction of the third valve hole 40.

The central axis of the outlet passageway 96 is offset from the centralaxis of the third valve hole 40. An upstream end of the outletpassageway 96 opens laterally to the third valve hole 40.

A filter 98 is arranged in the outlet port 44. If an abrasive powder,for example, is generated and becomes mixed in the working oil in thebody 54, the filter 98 removes the abrasive powder from the working oilwhen the working oil flows out of the outlet port 44. Therefore, theworking oil, which is made clean by the filter 98, is discharged fromthe outlet port 44.

The relief valve 46 has an introduction port 100 arranged above andjoined to the outlet passageway 96. In other words, the outletpassageway 96 branches into the outlet port 44 and the introduction port100. The introduction port 100 is placed in a closed condition when thespherical valve element 48 of the relief valve 46 is seated on the valveseat 52. The introduction port 100 comprises a constricted passageway,the inside diameter of which is smaller than the outlet passageway 96.

More specifically, as shown in FIGS. 9 and 10, a tubular boss 102, whichserves as a body of the relief valve 46, protrudes integrally from theclosed end face of the body 54 at a position above the third valve hole40. The spherical valve element 48 and the closing spring 50 are housedin a relief chamber 104, which is defined in the tubular boss 102.

Between the introduction port 100 and the relief chamber 104, the body54 includes an annular inner wall surface, which protrudes radiallyinward to form the valve seat 52, and a guide 106 having an innercircumferential wall surface for guiding the spherical valve element 48.A relief hole 108 is defined through the body 54 immediately above thevalve seat 52. The relief hole 108 extends in a straight linehorizontally from the inner circumferential wall surface of the guide106 to an outer wall surface of the tubular boss 102. Thus, the reliefhole 108 is defined as a horizontal hole, and comprises a constrictedpassageway similar to the introduction port 100.

The spherical valve element 48 has a surface that is exposed outside ofthe guide 106. An end of the closing spring 50 is seated on the exposedsurface of the spherical valve element 48. The other end of the closingspring 50 is held against (in contact with) an inner surface of a cover110, which covers the upper surface of the tubular boss 102.

As shown in FIG. 9 and FIG. 11, in which the cover 110 and the closingspring 50 are omitted from illustration, three angularly spaced recesses112 are defined in a bottom wall of the relief chamber 104. Each of therecesses 112 is substantially semicircular in shape. The guide 106includes regions in which the recesses 112 are defined, and such regionshave a dimension in the heightwise direction (Z direction), which issmaller than other regions of the guide 106. Stated otherwise, the guide106 has vertical grooves defined therein that serve as the recesses 112(see FIG. 9).

The tubular boss 102 has an outer side wall surface including a verticalwall surface (engaging portion) 114 (see FIG. 11), which is shaped insuch a manner that a portion of the outer side wall is cut off from theupper end toward the body 54.

A joining tubular boss 118 protrudes integrally from the body 54adjacent to the tubular boss 102, at a position above the third valvehole 40 (i.e., the control valve 16) on the closed end face of the body54. The joining tubular boss 118 has an internally threaded surface 120(see FIGS. 9 and 11) and is joined to the tubular boss 102 by a rib 122,which is thinner than the tubular boss 102 and the joining tubular boss118 (see FIG. 11). The rib 122 also protrudes integrally from the body54.

The cover 110 is essentially in the form of a rectangular plate (seeFIGS. 2 and 9), and is attached to the joining tubular boss 118 incovering relation to upper surfaces of the tubular boss 102 and thejoining tubular boss 118. The cover 110 has a through hole 124 (see FIG.9) defined therein. A fastening bolt 126 that serves as a fastener isinserted through the through hole 124 and is threaded into theinternally threaded surface 120 of the joining tubular boss 118, therebysecuring the cover 110 in position.

The cover 110 includes a hook 128 (see FIGS. 2 and 9) that is formed ina protruding manner and hangs from one end thereof. The hook 128 isengaged by the vertical wall surface 114 of the tubular boss 102,thereby preventing the cover 110 from turning. Therefore, the verticalwall surface 114 functions as a lock for locking the hook 128 of thecover 110 in position.

The height of the tubular boss 102 is smaller than that of the joiningtubular boss 118. Consequently, when the cover 110 is fastened to theupper end of the joining tubular boss 118, a small clearance 130 (seeFIG. 9) remains between the cover 110 and the upper surface of thetubular boss 102. The relief chamber 104 is vented to atmosphere throughthe clearance 130. In this manner, working oil, which has leaked intothe relief chamber 104, is discharged from the clearance 130.

As shown in FIGS. 2, 3, and 10, the body 54 includes a plurality offirst insertion holes 132 (fastener insertion holes) and secondinsertion holes 134 (fastener insertion holes) defined in athicknesswise direction thereof. Joining bolts that serve as fastenerspass through the first insertion holes 132 and the second insertionholes 134. More specifically, seven first insertion holes 132 arepositioned near the first valve hole 24 and the third valve hole 40, andfour second insertion holes 134 are positioned near the second valvehole 34.

As shown in FIGS. 2 and 3, the distance (pitch) P1 between the firstinsertion holes 132 along the axial direction (Y direction) is less thanthe distance (pitch) P2 between the second insertion holes 134 along theaxial direction (Y direction). Stated otherwise, the plural firstinsertion holes 132 are spaced relatively densely, whereas the pluralsecond insertion holes 134 are spaced relatively coarsely.

The hydraulic pressure control apparatus 10 according to the presentembodiment basically is constructed as described above. Operations andadvantages of the hydraulic pressure control apparatus 10 will bedescribed below.

The body 54 of the hydraulic pressure control apparatus 10 may beproduced by die casting, for example. The tubular boss 102, the rib 122,and the joining tubular boss 118 may be formed so as to extend along adirection (Z direction) in which the casting die assembly is opened.Therefore, the body 54 can be produced with ease.

The relief valve 46 is assembled in the body 54 in the following manner.The spherical valve element 48 and the closing spring 50 are inserted inthis order into the tubular boss 102, i.e, the relief chamber 104, andthereafter, the cover 110 is attached so as to cover the tubular boss102 and the upper surface of the joining tubular boss 118. At this time,the through hole 124 is aligned with the internally threaded surface120, and the hook 128 is placed in engagement with the vertical wallsurface 114.

Then, the fastening bolt 126 is inserted into the through hole 124 andthreaded into the internally threaded surface 120, thereby fastening thecover 110 in position. At this time, since the hook 128 is placed inengagement with the vertical wall surface 114, the cover 110 isprevented from turning around the fastening bolt 126. Since the cover110 is prevented from turning by the vertical wall surface 114 thatengages the hook 128, the cover 110 can easily be installed on the body54, or in other words, assembly of the relief valve 46 can befacilitated.

As described above, the relief valve 46 can easily be assembled simplyby inserting the spherical valve element 48 and the closing spring 50into the tubular boss 102, followed by fastening the cover 110 to thejoining tubular boss 118 with the fastening bolt 126.

The hydraulic pressure control apparatus 10 is mounted on anon-illustrated companion member with a separate plate 136 interposedtherebetween. The hydraulic pressure control apparatus 10 is connectedto the companion member by joining bolts, not shown, which are insertedthrough the first insertion holes 132 and the second insertion holes134, such that the open end face having the first oil passageway 20, thesecond oil passageway 23, and the third oil passageway 36 definedtherein (see FIG. 3) is closed. More specifically, the side of the oilpassageway wall 61 is arranged in facing relation to the companionmember. Generally, the open end face shown in FIG. 3 is directedupwardly, whereas the closed end face shown in FIG. 10 is directeddownwardly. A controller such as an ECU or the like is connectedelectrically to the solenoid 30.

The hydraulic pressure control apparatus 10 operates in the followingmanner.

At first, the hydraulic pressure control apparatus 10 is supplied withworking oil under a predetermined initial oil pressure (line pressure)by a non-illustrated oil pump. The working oil passes through the filter62 (see FIG. 5), which removes foreign matter, and thereafter, theworking oil is introduced from the inlet port 18 into the body 54, andflows along the inlet passageway 64 in the thicknesswise direction ofthe body 54.

Since the communication passageway 66 is defined at an intermediateposition along the heightwise direction of the inlet passageway 64, theworking oil flows through the communication passageway 66, and thenflows through the orifice 67. The working oil is limited in flow rateand increased in speed by the orifice 67, and then, the working oilflows into the first oil passageway 20.

If the communication passageway 66 were defined as a horizontal holeextending along the axial direction Y, then the distance along thecommunication passageway 66 between the inlet passageway 64 and thefirst oil passageway 20 would be large, and the length of the body 54would necessarily increase along the thicknesswise direction (Zdirection) thereof. In contrast, according to the present embodiment,the communication passageway 66, which is defined downstream of thefilter 62, is inclined with respect to the thicknesswise direction (Zdirection) of the body 54, and the downstream end thereof opens upwardlyat the starting end of the first oil passageway 20. Consequently, sincethe length of the body 54 in the thicknesswise direction (Z direction)is smaller than if the communication passageway 66 were defined as ahorizontal hole, the body 54 is reduced in size.

Further, since the orifice 67 is arranged downstream of the filter 62,the flow speed of the working oil increases after the working oil haspassed through the filter 62. After the working oil passes through theorifice 67 and is increased in speed, the working oil does not contactthe filter 62, because the orifice 67 is not arranged upstream of thefilter 62. Consequently, an excessive burden is not imposed on thefilter 62.

The working oil, which has entered the first oil passageway 20, flowsalong the first oil passageway 20. Since the first line pressure inletport 68 and the second line pressure inlet port 70 are arrangedsuccessively downstream in this order along the first oil passageway 20,the working oil enters the third valve hole 40 and the first valve hole24.

The working oil, which has entered into the first valve hole 24, will bedescribed below. In the first valve hole 24, as shown in FIGS. 1 and 4,the first valve rod 22 of the regulator valve 12 is resiliently biasedby the first pressure regulating spring 26. When the first valve rod 22stops at a position at which the resilient biasing force of the firstpressure regulating spring 26 and the feedback oil pressure that acts onthe first valve rod 22 are held in equilibrium, the oil pressure of theworking oil is reduced, i.e., the working oil is depressurized.

The working oil, which has entered into the third valve hole 40, issupplied under the line pressure to the control valve 16, as will bedescribed later.

The working oil, which has been depressurized in the first valve hole 24by the regulator valve 12, is released through the first valve holeoutlet hole 72 into the second oil passageway 28. The working oil flowsalong the second oil passageway 28, and then flows from the second valvehole inlet hole 74 into the second valve hole 34 (see FIG. 3).

According to the present embodiment, since the regulator valve 12 andthe solenoid-operated valve 14 are arranged adjacent to each other, thesecond oil passageway 28, which keeps the first valve hole outlet hole72 (the outlet port of the regulator valve 12) and the second valve holeinlet hole 74 (the inlet port of the solenoid-operated valve 14) influid communication with each other, can be of a short straight shape.Therefore, the working oil, which is released out of the first valvehole 24, can quickly reach the second valve hole 34, thereby increasingthe response speed.

The working oil, which has entered into the second valve hole 34 throughthe regulator valve 12, i.e., the depressurized working oil, applies aninput oil pressure to the solenoid-operated valve 14. A controller suchas an ECU or the like supplies a command electric current to thesolenoid 30 of the solenoid-operated valve 14. In response to thecommand electric current, the solenoid 30 applies a thrust force, whichcorresponds to the value of the command electric current, to the secondvalve rod 32.

As a result, the feedback oil pressure, the thrust force from thesolenoid 30, and the resilient biasing force from the second pressureregulating spring 35 all act on the second valve rod 32. The secondvalve rod 32 is held in a position at which such forces are kept inequilibrium, further regulating the oil pressure of the working oil, orgenerally depressurizing the working oil, in order to attain apredetermined solenoid pressure.

During this time, a portion of the working oil is released from thesecond valve hole 34 and through the second communication hole 90, andis stored in the spring chamber 35 a and the second pool 88 (see FIG.8). The working oil, which is stored in the spring chamber 35 a and thesecond pool 88, functions as a damper on the second valve rod 32. Morespecifically, since the working oil is stored in the second pool 88which is formed on the upper side of the spring chamber 35 a withrespect to the direction of gravity, the working oil flows from thespring chamber 35 a into the second pool 88, or vice versa through thedamper orifice 91 upon movement of the second valve rod 32. Therefore,the oil pressure that acts on the second valve rod 32 is prevented fromoscillating.

When working oil in excess of a certain amount flows into the secondpool 88, the excessive working oil overflows the overflow wall 94 and isdrained from the second drain hole 92.

The working oil, the oil pressure of which has been regulated to attainthe solenoid pressure, is released from the second valve hole outlethole 84 into the third oil passageway 36 (see FIGS. 1 and 3).Furthermore, the working oil flows along the third oil passageway 36 andenters the third valve hole 40 through the solenoid pressure inlet hole86. Thus, the control valve 16 is supplied with working oil under theline pressure introduced from the inlet port 18, and further is suppliedwith working oil released from the solenoid-operated valve 14 under thesolenoid pressure.

Consequently, the resilient biasing force from the third pressureregulating spring 42, the solenoid pressure (pilot pressure), and thefeedback oil pressure that acts on the control valve 16 are applied tothe third valve rod 38 of the control valve 16. The third valve rod 38is held in a position at which such forces are kept in equilibrium,thereby regulating the oil pressure of the working oil, ordepressurizing the working oil, which is supplied under the linepressure to the control valve 16. At this time, the working oil isregulated to attain a predetermined oil pressure, e.g., a predeterminedclutch pressure (actuating pressure).

The outlet passageway 96 lies perpendicularly across the third valvehole 40. Therefore, the working oil under the clutch pressure flowsthrough the outlet passageway 96 that extends along the thicknesswisedirection of the body 54, and is released from the outlet port 44. Theworking oil released from the outlet port 44 is supplied to anon-illustrated clutch. If an abrasion powder is generated in the firstvalve hole 24, the second valve hole 34, or the third valve hole 40 andis carried by the working oil, the abrasion powder becomes trapped bythe filter 98 arranged in the outlet port 44. Therefore, the clutch canbe supplied with clean working oil.

As described above, the working oil under the clutch pressure flows onlyalong the thicknesswise direction of the body 54, and not through any ofthe oil passageways defined in the open end face. In other words, thereis no need to provide oil passageways in the open end face for passageof the working oil under the clutch pressure.

According to the present embodiment, the solenoid-operated valve 14 andthe control valve 16 are juxtaposed with the regulator valve 12interposed therebetween. Since the regulator valve 12 and the controlvalve 16 lie parallel to each other, the length of the first oilpassageway 20 that interconnects the regulator valve 12 and the controlvalve 16 can be reduced.

Since the first oil passageway 20 and the second oil passageway 28 areshortened for the reasons described above, the total length of the oilpassageways is reduced. Consequently, the body 54 and hence thehydraulic pressure control apparatus 10 as a whole can be reduced insize.

Furthermore, since the regulator valve 12, the solenoid-operated valve14, and the control valve 16 are juxtaposed with their axes arrayedalong the widthwise direction (X direction) of the body 54, thehydraulic pressure control apparatus 10 is not increased in size alongthe thicknesswise direction (Z direction) of the body 54. Alongtherewith, the hydraulic pressure control apparatus 10 can also be madesmaller in size.

Inasmuch as the first oil passageway 20 and the second oil passageway 28are shortened in length, the working oil reaches the first valve hole24, the second valve hole 34, and the third valve hole 40 quickly.Therefore, the regulator valve 12, the solenoid-operated valve 14, andthe control valve 16 produce an improvement in response speed.

A portion of the working oil, which has entered into the third valvehole 40, is released from the third valve hole 40 and through the firstcommunication hole 78, and is stored in the first pool 76. When workingoil in excess of a certain amount flows into the first pool 76, theexcessive working oil overflows the overflow wall 82 and is drained fromthe first drain hole 80.

As can be understood from the above description, the hydraulic pressurecontrol apparatus 10 allows the regulator valve 12 and the control valve16 to be supplied with working oil under high pressure. According to thepresent embodiment, the pitch P1 between the first insertion holes 132near the first valve hole 24 and the third valve hole 40 under highpressure is reduced, whereas the pitch P2 between the second insertionholes 134 near the second valve hole 34 under relatively low pressure isincreased (see FIGS. 3 and 10). Therefore, it is necessarily the casethat the distance between the joining bolts near the regulator valve 12and the control valve 16 is smaller than the distance between thejoining bolts near the solenoid-operated valve 14.

When the hydraulic pressure control apparatus 10 is installed on thecompanion member by the joining bolts, a greater surface pressure can beapplied to the oil passageway wall 61 near the regulator valve 12 andthe control valve 16. In other words, the oil passageway wall 61 nearthe regulator valve 12 and the control valve 16 is firmly held incontact with the companion member. Consequently, working oil isprevented from leaking from between the companion member and the areanear the third valve hole 40 in the body 54.

The distance between the joining bolts near the solenoid-operated valve14 is greater than the distance between the joining bolts near theregulator valve 12 and the control valve 16. Further, thesolenoid-operated valve 14 is supplied with working oil and dischargesthe working oil under a relatively low pressure. Therefore, although alarge pressure is not applied between the oil passageway wall 61 nearthe solenoid-operated valve 14 and the companion member, the working oilis prevented sufficiently from leaking from between the companion memberand the area near the second valve hole 34 in the body 54.

The tubular boss 102, and the rib 122 and the joining tubular boss 118are arranged in respective areas above the first valve hole 24 and thethird valve hole 40. The tubular boss 102, and the rib 122 and thejoining tubular boss 118 serve to increase the mechanical strength ofareas in the vicinity of the first valve hole 24 and the third valvehole 40. In other words, such areas of the body 54, which are held underrelatively high pressure, have sufficient mechanical strength.

As described above, while the working oil is flowing, since the outletpassageway 96 also is held in fluid communication with the introductionport 100 of the relief valve 46 (see FIG. 9), the working oil, which isreleased from the third valve hole 40 into the outlet passageway 96,also flows into the introduction port 100. Since the introduction port100 is connected to the outlet passageway 96 and extends along thethicknesswise direction of the body 54, the working oil that is directedtoward the relief valve 46 flows only in the thicknesswise direction ofthe body 54. In other words, there is no need to provide oil passagewaysin the open end face of the body 54 for guiding the working oil towardthe relief valve 46. This also contributes to reducing the total lengthof all of the oil passageways, and hence leads to a reduction in thesize of the hydraulic pressure control apparatus 10, as well asincreasing the response speed of the relief valve 46.

As described above, the pressing force from the working oil and theresilient biasing force from the closing spring 50 both act on thespherical valve element 48 of the relief valve 46. If the resilientbiasing force from the closing spring 50 is greater than the pressingforce (i.e., the clutch pressure) from the working oil, the sphericalvalve element 48 remains seated on the valve seat 52. The sphericalvalve element 48 is resiliently biased toward the valve seat 52 by theclosing spring 50. At this time, the relief valve 46 is closed.

Normally, the clutch pressure is set to a level which is less than theresilient biasing force from the closing spring 50. Since the reliefvalve 46 remains in a closed condition, the working oil in the body 54flows only along a route from the inlet port 18 to the outlet port 44.

For inspecting the relief valve 46 in order to check whether or not therelief valve 46 is operating normally, the first drain hole 80 initiallyis closed by a non-illustrated rod-shaped inspection tool, for example.Then, the clutch pressure from the outlet port 44 is increased until theclutch pressure exceeds the resilient biasing force from the closingspring 50, i.e., up to a predetermined threshold pressure. If the reliefvalve 46 is opened under the threshold pressure, the relief valve 46 isjudged as operating norrally. On the other hand, if the relief valve 46remains closed under the threshold pressure, the relief valve 46 isjudged as malfunctioning.

When the relief valve 46 operates normally, the relief valve 46 isopened in the following manner.

If the working oil that flows into the introduction port 100 is appliedunder a pressure that is equal to or greater than the thresholdpressure, e.g., is applied at the threshold pressure, the sphericalvalve element 48 is displaced by the working oil and becomes unseatedfrom the valve seat 52. Thus, the introduction port 100 is opened,thereby opening the relief valve 46. Upon displacement of the sphericalvalve element 48, the spherical valve element 48 is guided by the guide106, and the closing spring 50 is compressed.

The working oil flows through the relief hole 108, which is defined as ahorizontal hole, and is borne by a semispherical portion of thespherical valve element 48, which faces toward the introduction port100. Since the relief hole 108 is defined between the valve seat 52 andthe guide 106, or immediately above the valve seat 52, the working oilessentially is not directed upwardly into the relief chamber 104, butrather is quickly discharged out of the body 54 through the relief hole108.

When the working oil is borne by the semispherical portion of thespherical valve element 48, the spherical valve element 48 is displacedor lifted a predetermined distance to a certain position and is held inthe displaced position. The displaced position is a location at whichthe force that the spherical valve element 48 bears from the working oilin the guide 106, and the resilient biasing force from the closingspring 50 are kept in equilibrium. Therefore, the displaced positionwhere the spherical valve element 48 is held can be adjusted byadjusting the force that is borne by the spherical valve element 48 fromthe working oil in the guide 106, and the resilient biasing force fromthe closing spring 50. Preferably, the displaced position where thespherical valve element 48 is held is in the vicinity of the valve seat52.

The force that is borne by the spherical valve element 48 due to theworking oil in the guide 106 can be adjusted by adjusting the diametersof the respective constricted passageways provided in the introductionport 100 and the relief hole 108. For example, the diameter of theconstricted passageway provided in the introduction port 100 should besmaller than the diameter of the constricted passageway provided in therelief hole 108.

As described above, since the entire surface of the semisphericalportion of the spherical valve element 48 bears the working oil, and therelief hole 108 is defined immediately above the valve seat 52, thespherical valve element 48 is displaced or lifted by a small distance.The closing spring 50 may be of a small size, because the closing spring50 only needs to be compressed sufficiently to allow the spherical valveelement 48 to be displaced by the aforementioned small distance.Consequently, the height of the tubular boss 102, in which the reliefchamber 104 housing the closing spring 50 is defined, i.e., thedimension of the tubular boss 102 along the Z direction, is small. Sincethe height of the rib 122 and the height of the joining tubular boss 118necessarily are small, the relief valve 46 and the area surrounding therelief valve 46, and hence the hydraulic pressure control apparatus 10as a whole, can be reduced in size.

The three recesses 112, which are defined in the bottom wall of therelief chamber 104, serve as vertical grooves in the guide 106. When theworking oil is applied at a higher pressure, tending to lift thespherical valve element 48 beyond the predetermined distance, theworking oil leaks from the recesses 112, thereby preventing thespherical valve element 48 from being further lifted.

Since the spherical valve element 48 is prevented from being furtherlifted, the distance by which the closing spring 50 is deformed orcompressed is reduced. As a result, the closing spring 50 and hence thehydraulic pressure control apparatus 10 can be reduced in size. Therecesses 112 are defined at a position slightly above the displacedposition at which the spherical valve element 48 is held. Accordingly,the recesses 112 are defined at a position from which the working oilcan be leaked.

As the working oil flows through the hydraulic pressure controlapparatus 10, the hydraulic pressure control apparatus 10 produces thesolenoid pressure from one of the branched line pressures, and using thesolenoid pressure as a pilot pressure, produces the clutch pressure fromthe other branched line pressure.

If the clutch pressure, which is produced in the foregoing manner, islower than the threshold pressure, the relief valve 46 remains closed.On the other hand, if the clutch pressure becomes equal to or greaterthan the threshold pressure, the spherical valve element 48 is liftedoff of the valve seat 52, thereby opening the relief valve 46. As aresult, the working oil is discharged from the relief hole 108.Accordingly, the working oil is prevented from being applied to theclutch under a pressure that is equal to or greater than a predeterminedpressure, thereby protecting the clutch from undue damage.

The present invention is not limited to the above embodiment. Rather,various changes and modifications may be made to the embodiment withoutdeparting from the scope of the present invention.

For example, the working oil, the pressure of which is regulated by thehydraulic pressure control apparatus 10, may be supplied to otherdevices than a clutch. More specifically, the pressure-regulated workingoil may be used as an actuating oil for pulleys that are used incontinuously variable transmissions (CVTs).

What is claimed is:
 1. A hydraulic pressure control apparatuscomprising: a first pressure regulating valve configured to reduce aninitial oil pressure of a working oil introduced from an inlet port; asolenoid-operated valve supplied with an electric current and a reducedoil pressure, the oil pressure reduced by the first pressure regulatingvalve, the solenoid-operated valve configured to convert the reduced oilpressure into a solenoid pressure in accordance with the suppliedelectric current; a second pressure regulating valve supplied with thesolenoid pressure from the solenoid-operated valve, the second pressureregulating valve converting the initial oil pressure of the working oilintroduced from the inlet port into an actuating pressure in accordancewith the solenoid pressure; and a relief valve arranged in a working oilpassage, the relief valve being operable to release the working oil outof the working oil passage when the pressure of the working oil in theworking oil passage becomes equal to or greater than a predeterminedthreshold value of the relief valve, wherein: the first pressureregulating valve, the solenoid-operated valve and the second pressureregulating valve share a single body; the second pressure regulatingvalve has an outlet passageway in the body; the relief valve has a valvebody, and the valve body is integrally molded onto the body andprotrudes from an end face of the body at a position corresponding tothe outlet passageway; the body includes a joining boss, the joiningboss is integrally molded onto the body and protrudes from the end faceof the body at a position corresponding to the second pressureregulating valve, and the joining boss extends parallel to the valvebody of the relief valve; the valve body and the joining boss are joinedto each other by a rib, the rib being thinner than the valve body andthe joining boss; and the joining boss and the valve body haverespective upper surfaces, the upper surfaces are covered by a cover,and the cover is connected by a fastener to the joining boss.
 2. Thehydraulic pressure control apparatus according to claim 1, wherein thevalve body accommodates a valve element and a resilient member therein,the resilient member has an end seated onto the cover, and the valveelement is resiliently biased so as to be seated on a valve seat by theresilient member.
 3. The hydraulic pressure control apparatus accordingto claim 2, wherein the valve element is of a spherical shape.
 4. Thehydraulic pressure control apparatus according to claim 1, wherein thejoining boss has a protruding height greater than that of the valvebody, and the cover is spaced from the upper surface of the valve body.5. The hydraulic pressure control apparatus according to claim 1,wherein the cover has a hook, and the valve body has an engaging portionthat engages with the hook.